The present invention relates generally to spray painting systems of the type having one or more spray stations. In each spray station there is at least one moveable spray gun or nozzle and conveyor means for transporting objects of diverse geometry, such as automobile bodies, past the spray nozzle. More particularly, the invention is directed to an improved control system for automatically regulating the operation of a plurality of spray gun assemblies in accordance with information contained in a memory which relates to the size and style of the object to be sprayed as well as the desired color. Those concerned with the development of a paint spray control system have long recognized the need for developing a spray control which may be pre-programmed to include information relating to the objects to be sprayed that will be retained in the memory indefinitely so as to be recalled whenever it is desired.
Several known prior art spray control systems are able to sense the horizontal direction and position of an object to be sprayed in an area remote from the spray station. One such control system which also includes a means for measuring the vertical height of the part to be sprayed is disclosed in U.S. Pat. No. 3,593,308, issued July 13, 1971 to John C. Fagan and assigned to AMTRON, INC. The spray control system disclosed in this patent includes a means for developing a digitized signal representative of the horizontal and vertical dimension of an object to be sprayed. The digitized information is then fed into a shift register and the output of the shift register actuates spray guns on the spray gun assembly. Means are also provided for moving the spray gun assembly between two vertical limits. In order to accurately measure the vertical dimensions of the part, the above-identified patent utilizes a plurality of shift registers, one shift register being associated with each incremental vertical zone. For example, if ten vertical zones are used, it is necessary to utilize 10 shift registers. After the part to be sprayed has passed through the spray station, all information relating to its size and shape is destroyed.
A second spray control system is disclosed in U.S. Pat. No. 3,646,521, issued Feb. 29, 1971 to Virgil E. Porter and assigned to AMTRON, INC. In this latter patent, a spray control system is provided which utilizes a single memory storage matrix for storing a digitized information signal which is related to the dimensions of the object. The memory storage matrix replaces the need for the plurality of shift registers utilized in U.S. Pat. No. 3,593,308, described above. In this patent, after the part to be sprayed has passed through the spray station, the information stored in the memory is destroyed.
In both of the above described prior art paint spray applications, the spray guns which are utilized in each spray station are continuously vertically reciprocated. The control system, whether it be the shift register or the matrix memory, turns on the guns at the appropriate vertical position if a part is present at that height. If a part to be sprayed is not present at that height, the guns remain off.